It is not known to evolve into or from any other Pokémon. However, as of Generation IV, Unown has 28 derivative shapes. There are 26 English alphabet characters, plus two punctuation marks: ? (question mark) and ! (exclamation mark). That shape is determined by its personality value.

Biology

Physiology

It is a floating, flat Pokémon with appendages that make it resemble letters. It is black all over and has a large, single eye.

Gender differences

This Pokémon is genderless.

Different forms

Unown has 28 different forms, one for each letter of the alphabet, as well as '!' and '?'. These are chronicled in the Unown Dex.
The '!' and '?' forms were not introduced until Generation III.

Special abilities

Unown's only known move in battle is the enigmatic Hidden Power. In the anime, they are capable of reading the thoughts of other lifeforms (which isn't a unique ability in itself). However, great numbers of them are capable of warping reality to suit the dreams and wishes of whoever is in control.

Behavior

Unown can make telepathic contact with humans (and many other creatures also). Unown have a timidness that rarely makes them venture outside of their dimension.

An Unown fell out of the Unown dimension in Address Unown. After it was healed by the group, it helped defend against Team Rocket and its mind merged with that of Ash's Larvitar so that the group could help it to address its inner pain.

Unown later appear in Template:PSV, having been awakened by Sird from the Tanoby Ruins to use as a distraction while she fought Lorelei. The Unown later appear again throughout the volume, being employed by Team Rocket as living security cameras while impeding the progress of Red, Blue and Green.

It also appeared in DP saga when Diamond, Pearl and Berlitz were visiting Solaceon City. Diamond and Pearl befriended two Unowns (D and P) who behaved like them.

In the TCG

Other appearances

When one Unown is released from a Poké Ball it will fly off the screen. It then returns with a large swarm similar to what Beedrill did in the original Super Smash Bros. The only difference is that Beedrill only attack from left or right while Unown can come from any direction. Any opponent caught in this is damaged and juggled.

There are also a number of Unown Pokéfloats. In the second half of the cycle, a number fly across the screen. Towards the end of the cycle, staying on the stage relies on hopping between the Unown.

Unown's forms

Trivia

In Spell of the Unown, Professor Oak had some pictures of unreleased Unown on his computer. They resemble a few Greek alphabet letters, especially σ (lowercase sigma), Σ (capital sigma), π (pi) and Ω (omega). The top-middle Unown may be also a variation of an ancient Egyptian symbol of protection, the Eye of Horus. This may lead to the conclusion that there are more forms of Unown, being the prototypes of other known (or unknown) alphabets.

In Generation II, the Unown appear to be able to generate a radio signal.

This makes it the first non-legendary to be in a central role in a Pokémon movie.

Unown and Ditto are the only two non-legendary, non-baby Pokémon that cannot breed with Ditto.

Despite being in the book of legendary Pokémon, Unown is not considered a legendary Pokémon.

Only the two punctuation Unown have half-closed eyes, the letters have fully open eyes.

If a player does not have Unown's Pokédex data on a Generation II game when in Oak's lab in Pokémon Stadium 2, Unown's Pokédex number is listed as Template:P2 instead of 201. This happens regardless of which Pokédex display mode is selected.

Origin

Their appearances are corruptions of the modern Latin alphabet. The shapes of the Unown are used like runes in the Pokémon world, although in Generation III their place has been taken by Braille.

Name origin

Unown's name is a misspelling of the word unknown.
Its German name, Icognito, comes from Ikone and Inkognito, one who has their identity concealed. Its French name, Zarbi, comes from the word bizarre in verlan, a youth language.